Osteoporosis is one of the unfortunate sequelae of increased life expectancy and is a chronic disorder that predisposes individuals to fractures. Approximately 10 million Americans alone have osteoporosis and about 34 million more have an increased risk of developing osteoporotic fractures because of low bone mass. Thus, just over half of the people in the U.S. that are over 50 years old are at risk. Recent advances have led to the introduction of many drugs to treat osteoporosis. However, many patients still have an inadequate clinical outcome and remain at risk.
Studies of osteoporosis are likely to consider the dynamics of bone remodeling; osteoclasts mediate bone resorption and osteoblasts mediate bone formation. Bone remodeling regulates calcium homeostasis in that, bone resorption by the osteoclasts releases stored calcium into the systemic circulation, and bone formation by osteoblasts fixes circulating calcium in its mineral form. Disrupting this balance between bone resorption and formation can result in various bone pathologies in which bone mineral density (BMD) is reduced, bone micro architecture is disrupted, and the amount and variety of non-collagenous proteins in bone is altered.